Photosyntesis Tumbuhan

1. PHOTOSYNTHESIS

2. Photosynthesis
• An anabolic, endergonic, carbon dioxide
(CO2) requiring process that uses light energy
(photons) and water (H2O) to produce organic
macromolecules (glucose).
6CO2 + 6H2O  C6H12O6 + 6O2
glucose
SUN
photons

3. Question:
• Where does photosynthesis take place?

4. Plants
• Autotrophs: self-producers.
• Location:
1.Leaves
a. stoma
b. mesophyll cells
Stoma
Mesophyll
Cell
Chloroplast

5. Stomata (stoma)
• Pores in a plant’s cuticle through which
water and gases are exchanged between the
plant and the atmosphere.
Guard Cell
Guard Cell
Carbon Dioxide
(CO2)
Oxygen
(O2)

6. Mesophyll Cell
Cell Wall
Nucleus
Chloroplast
Central Vacuole

7. Chloroplast
• Organelle where photosynthesis takes place.
Granum
Thylakoid
Stroma
Outer Membrane
Inner Membrane

8. Thylakoid
Thylakoid Membrane
Thylakoid Space
Granum

9. Question:
• Why are plants green?

10. Chlorophyll Molecules
• Located in the thylakoid membranes.
• Chlorophyll have Mg+ in the center.
• Chlorophyll pigments harvest energy (photons)
by absorbing certain wavelengths (blue-420
nm and red-660 nm are most important).
• Plants are green because the green
wavelength is reflected, not absorbed.

11. Wavelength of Light (nm)
400 500 600 700
Short wave Long wave
(more energy) (less energy)

12. Absorption of Chlorophyll
wavelength
Absorption
violet blue green yellow orange red

13. Question:
• During the fall, what causes the leaves to
change colors?

14. Fall Colors
• In addition to the chlorophyll pigments, there are
other pigments present.
• During the fall, the green chlorophyll pigments
are greatly reduced revealing the other
pigments.
• Carotenoids are pigments that are either red or
yellow.

15. Redox Reaction
• The transfer of one or more electrons from
one reactant to another.
• Two types:
1. Oxidation
2. Reduction

16. Oxidation Reaction
• The loss of electrons from a substance.
• Or the gain of oxygen.
glucose
6CO2 + 6H2O  C6H12O6 + 6O2
Oxidation

17. Reduction Reaction
• The gain of electrons to a substance.
• Or the loss of oxygen.
glucose
6CO2 + 6H2O  C6H12O6 + 6O2
Reduction

18. Breakdown of Photosynthesis
• Two main parts (reactions).
1. Light Reaction or
Light Dependent Reaction
Produces energy from solar power
(photons) in the form of ATP and NADPH.

19. Breakdown of Photosynthesis
2. Calvin Cycle or
Light Independent Reaction or
Carbon Fixation or
C3 Fixation
Uses energy (ATP and NADPH) from light
rxn to make sugar (glucose).

20. 1. Light Reaction (Electron Flow)
• Occurs in the Thylakoid membranes
• During the light reaction, there are two
possible routes for electron flow.
A. Cyclic Electron Flow
B. Noncyclic Electron Flow

21. A. Cyclic Electron Flow
• Occurs in the thylakoid membrane.
• Uses Photosystem I only
• P700 reaction center- chlorophyll a
• Uses Electron Transport Chain (ETC)
• Generates ATP only
ADP + ATP
P

22. A. Cyclic Electron Flow
P700
Primary
Electron
Acceptor
e-
e-
e-
e-
ATP
produced
by ETC
Photosystem I
Accessory
Pigments
SUN
Photons

23. B. Noncyclic Electron Flow
• Occurs in the thylakoid membrane
• Uses PS II and PS I
• P680 rxn center (PSII) - chlorophyll a
• P700 rxn center (PS I) - chlorophyll a
• Uses Electron Transport Chain (ETC)
• Generates O2, ATP and NADPH

24. B. Noncyclic Electron Flow
P700
Photosystem I
P680
Photosystem II
Primary
Electron
Acceptor
Primary
Electron
Acceptor
ETC
Enzyme
Reaction
H2O
1/2O2 + 2H+
ATP
NADPH
Photon
2e-
2e-
2e-
2e-
2e-
SUN
Photon

25. B. Noncyclic Electron Flow
• ADP +  ATP
• NADP+ + H  NADPH
• Oxygen comes from the splitting of
H2O, not CO2
H2O  1/2 O2 + 2H+
(Reduced)
P
(Reduced
)
(Oxidized)

26. Chemiosmosis
• Powers ATP synthesis.
• Located in the thylakoid membranes.
• Uses ETC and ATP synthase (enzyme) to
make ATP.
• Photophosphorylation: addition of
phosphate to ADP to make ATP.

27. Chemiosmosis
H+ H+
ATP Synthase
H+ H+ H+ H+
H+ H+
high H+
concentration
H+
ADP + P ATP
PS II PS I
E
T
C
low H+
concentration
H+
Thylakoid
Space
Thylakoid
SUN
(Proton Pumping)

28. Calvin Cycle
• Carbon Fixation (light independent rxn).
• C3 plants (80% of plants on earth).
• Occurs in the stroma.
• Uses ATP and NADPH from light rxn.
• Uses CO2.
• To produce glucose: it takes 6 turns and
uses 18 ATP and 12 NADPH.

29. Chloroplast
Granum
Thylakoid
Stroma
Outer Membrane
Inner Membrane

30. Calvin Cycle (C3 fixation)
6CO2
6C-C-C-C-C-C
6C-C-C 6C-C-C
6C-C-C-C-C
12PGA
RuBP
12G3P
(unstable)
6NADPH 6NADPH
6ATP 6ATP
6ATP
C-C-C-C-C-C
Glucose
(6C)
(36C)
(36C)
(36C)
(30C)
(30C)
(6C)
6C-C-C 6C-C-C
C3
glucose

31. Calvin Cycle
• Remember: C3 = Calvin Cycle
C3
Glucose

32. Photorespiration
• Occurs on hot, dry, bright days.
• Stomates close.
• Fixation of O2 instead of CO2.
• Produces 2-C molecules instead of 3-C
sugar molecules.
• Produces no sugar molecules or no ATP.

33. Photorespiration
• Because of photorespiration: Plants have
special adaptations to limit the effect of
photorespiration.
1. C4 plants
2. CAM plants

34. C4 Plants
• Hot, moist environments.
• 15% of plants (grasses, corn, sugarcane).
• Divides photosynthesis spatially.
• Light rxn - mesophyll cells.
• Calvin cycle - bundle sheath cells.

35. C4 Plants
Mesophyll Cell
CO2
C-C-C
PEP
C-C-C-C
Malate
ATP
Bundle Sheath Cell
C-C-C
Pyruvic Acid
C-C-C-C
CO2
C3
Malate
Transported
glucose
Vascular
Tissue

36. CAM Plants
• Hot, dry environments.
• 5% of plants (cactus and ice plants).
• Stomates closed during day.
• Stomates open during the night.
• Light rxn - occurs during the day.
• Calvin Cycle - occurs when CO2 is present.

37. CAM Plants
Night (Stomates Open) Day (Stomates Closed)
Vacuole
C-C-C-C
Malate
C-C-C-C
Malate Malate
C-C-C-C
CO2
CO2
C3
C-C-C
Pyruvic acid
ATP
C-C-C
PEP
glucose

38. Question:
• Why would CAM plants close their
stomates during the day?